The repo implements some work by Gillman, Barnett and Martinsson on solving variable media Helmholtz scattering

I have been trying to implement this without much success. I will keep working on it. I will post results as I have them. To show that the merge process creates a resonable unitary operator, I post the eighenvalues of the same.

Eigenvalues of the ItI map of the root node:

![Eigenvalues][./eigen_R.png]